Air-arming pyro delay fuze



[56] References Cited UNITED STATES PATENTS 2,073,250 3/1937 Morpeth et a1. 102/79 2,900,908 8/1959 Burrell 102/79 Primary Examiner-Benjamin A Borchelt Assistant Examiner-Thomas H. Webb Attorney-E. J. Brower and Roy Miller ABSTRACT: Fuze which fires a delay train when an air dropped ordnance device reaches predetermined spin speed and is also sensitive to omnidirectional impact to fire an instantaneous train in event of failure of the delay train. Characterized by a rotor, centrifugal responsive weights for unlocking the rotor, a spring for rotating the rotor and mechanism for preventing premature firing of both trains until the ordnance device attains the predetermined spin speed.

Edgar J. Abt Hopkins, Minnesota [2]] Appl. No. 753,190

Aug. 16, 1968 [45] Patented Dec. 8, 1970 By mesne assignments, to the United States of America as Represented by the Secretary of the Navy.

8 Claims, 8 Drawing Figs.

United States Patent [72] Inventor [22] Filed [73] Assignee [54] AIR-ARMING PYRO DELAY FUZE [51] F42c 15/18, F42c 15/24 [50] FieldofSearch............................................

PATENTED DEC 8 I976- snm 1 or 2 EDGAR J. ABT

V. C. MULLER ROY MILLER ATTORNEYS.

AIR-ARMING PYRO DELAY FUZE BACKGROUND OF THE INVENTION It has been the practice to drop clusters of bomblets from aircraft which arm and fire a predetermined time after being dropped. In a recent development, the bomblets were spun by the airstream about an axis of the bomb to improve their stability. It was found desirable to utilize this spinning to arm the bomb to thus ensure that activation did not occur until the bomb was a safe distance from the aircraft. Also, in the event of failure of activation of the bomb, while above the ground, it was found desirable to activate it upon-ground impact.

DESCRIPTION OF THE DRAWING FIG. 1 is a section taken on line 1-1, FIG. 2,

FIG. 2 is a section taken on line 2-2, FIG. 1,

FIG. 3 is a section taken on line 3-3, FIG. 1,

FIG. 4 is an elevation in the direction of arrow 4, FIG. 2,

FIG. 5 is a side elevation, partly in section, of impact sensing mechanism, and

FIGS. 5A, 5B and 5C are like views illustrating various modes of operation.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring first to FIGS. 1 and 2, rotor housing includes a body portion 12 which is disposed within a cup shaped cover or shell 14 crimped at one end to the body portion. The upper end of the housing, as viewed in the drawing, contains an affixed plate 16 having a cutout 18 (FIG. 4), the purpose of which will subsequently be described, and the lower end contains a cup shaped closure 20 having a pair of diametrically opposed apertures 22, 24, the closure being filled with a suitable ignition charge 26 for an explosive (not shown) carried by the ordnance device to which the fuze is affixed. Body portion 12 is provided with a circumferential groove 28 which contains four equiangularly spaced arcuate lockweights 30 to each of which is affixed a locking pin 32 and a flat spring 34, the ends of which engage the cover and force the inner end of the locking pin into a slot or groove 36 in rotor 38. As will be apparent, the lockweights rotate with the housing but may move radially outward under centrifugal force to positions in which their locking pins disengage from the slots in the rotor permitting it to rotate relative to the housing.

Rotor 38 is provided with an arcuate groove 40 which contains a tension coil spring 42, one end of which is affixed to the rotor and the other end to the housing. Upon outward movement of the lockweights the spring rotates the rotor approximately 90 at which position apertures 44, 46, formerly misalined with apertures 22, 24, are now in alinement with same. Apertures 44, 46 contain suitable primer mixtures 45, 49 and percussion primers, one being of the delay type and the other of the instantaneous type.

A percussion primer striker 48 carrying a stab-type firing pin 50 is pivoted to the rotor by a pin 52 and urged toward firing position by a torsion spring 54. A book shaped sear 56 is pivoted to the rotor by a pin 58, one end of the sear engaging the striker, the other end having a pin 60 which engages a surface 61 on plate 16 when the rotor moves to final or arm position, releasing the sear and permitting the striker to move under urge of its spring into contact with the percussion primer, initiating the delay train which fires charge 26 after a predetermined delay.

The instantaneous firing mechanism, which is sensitive to impact, comprises an arm 62, having a slot 64 in which is disposed a pivot pin 66 affixed to the rotor, a compression coil spring 68 urging the arm against the pivot pin. A spoon shaped cavity 70 is disposed in the arm and contains a ball 72 which engages a shoulder or abutment 74 on the rotor. A sear 76 is also carried by the arm which engages a striker 78, like striker 48, and retains it in cocked position. One end of arm 62 is disposed in an arcuate slot 80 having stop surfaces 82, 84 at its ends. A stop pin 86 is affixed to the rotor and abuts surface 84 when the rotor rotates to arm position.

In the operation of the device the parts are assembled to the position illustrated with both strikers in cocked position. The lockweights now lock the rotor in a position such that apertures 22, 24 and apertures 44, 46 are misalined. Hook shaped sear 56 now abuts body portion 12, preventing its rotation and release of striker 48. Also, the outer end of arm 62 is in engagement with stop surface 82, preventing movement of the arm. When the ordnance device, which may be an air dropped bomblet, spins up to predetermined speed about the axis of the rotor the lockweights move radially outwardly, releasing the rotor for rotation under urge of rotor spring 42. As the rotor rotates counterclockwise, as viewed in FIG. 1, sear 56 moves adjacent slot and is now free to pivot. When it moves to near the end of the slot, pin 60 on the sear engages surface 61 on plate 16 (FIG. 4) and is cammed by it, rotating the sear and releasing the striker. Stop pin 86 then abuts surface 84 and limits the rotation of the rotor. After a predetermined delay the delay train initiates ignition or booster charge 26.

In the event the delay train or its mechanism should malfunction, the instantaneous firing mechanism will operate at impact. Referring now to FIG. 5, sear 76 is now retaining striker 78 in cock position. Assuming that the impact vector is in the direction of the arrow, FIG. 5A, the inertia of the ball cams the arm and releases the sear. As will be apparent, if the impact vector is diametrically opposed to the arrow it also earns the arm and releases the sear. If the impact vector is perpendicular to the arrow, FIG. 5A, or at various angles to it, the ball cams other surfaces of the arm and likewise releases the sear. If the impact vector is in the direction of the arrow, FIG. 5B, or within a small cone surrounding the arrow, the inertia of the ball moves the arm and releases the sear. If the impact vector is in the direction of the arrow, FIG. 5C, or within a small surrounding cone, the ball is blocked from movement by shoulder 74. In this case, the ball serves as a pivot and the inertia of a weight 86 on the arm pivots the arm and releases the sear. It thus becomes apparent that the impact vector may be in any direction to release the sear.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

I claim:

1. A fuze comprising:

a. a housing having a cylindrical bore;

b. a rotor journaled in the bore for rotation between an initial safe position and a final fire position;

c. a plurality of angularly spaced centrifugally actuated lockweights carried by the housing for rotation therewith;

(1. spring means for urging the lockweights radially inwardly into locking engagement with the rotor, the lockweights adapted to move radially outwardly out of locking engagement when the housing and :rotor attain a predetermined spin speed about the axis of the bore;

e. a rotor spring for rotating the rotor relative to the housing from safe to fire position and operative upon disengagement of the lockweights;

f. a delay powder train carried by the rotor, disposed parallel to its axis, adapted to move into axial registry with an aperture in the housing when the rotor moves to fire position;

g. a pivoted spring urged striker for initiating the delay train;

h. a pivoted sear engaging the striker and retaining it in cocked position;

i. said sear having a portion engageable with the housing for preventing it pivotal movements when the rotor is at safe position, the housing being so constructed to permit pivotal movement of the sear when the rotor moves away from safe position; and

j. an abutment on the sear engageable with the housing for rotating the sear and releasing the striker when the rotor rotates to fire position.

2. A fuze in accordance with claim 1, wherein the outer longitudinal surface of said housing is cylindrical and concentric with said bore, a circumferential groove in said surface, and a cylindrical cover surrounding same, said lockweights being arcuate in shape and disposed in said groove, and an elongated flat spring connected midway between its ends to a rotor lock pin disposed midway between the ends of each weight, the ends of the spring engaging said cover.

3. A fuze in accordance with claim 2, wherein one end of said rotor is provided with an arcuate groove, said spring means comprising a tension coil spring disposed in said groove, having one end secured to the rotor and the other end to the housing.

4. A fuze in accordance with claim 1 wherein said housing is provided with an end plate having a cutout portion forming a camming edge, said abutment on the sear comprising a laterally projecting pin engageable, with said camming edge.

5. A fuze in accordance with claim 1, including:

a second instantaneous powder train and a second pivoted spring urged striker for initiating the second powder train;

a second sear engaging the second striker and retaining it in cocked position; and

means for releasing the second sear from the second striker upon impact of the fuze with an object, in any direction of impact, whereby the instantaneous train is initiated in event of failure of initiation of the delay train.

6. A fuze in accordance with claim 5, wherein said second scar and the means for releasing it comprises:

a fixed substantially flat abutment surface on the housing;

an arm pivoted between its ends to the housing by a pin and slot connection;

a weight on the arm at one side of said connection;

a spoon-shaped surface on the arm at the other side of said connection;

a ball disposed between the abutment and the spoon-shaped surface;

a spring urging the surfaces aforesaid into contact; and

the construction and arrangement being such that in certain directions of impact the ball moves on the abutment, in contact with the spoon-shaped surface and earns the arm, rotating it about its pivotal connection, in another direction of impact the ball moves away from the abutment surface, its inertia rotating the am about the pivotal connection, and in another direction of impact the weight rotates the arm about the ball, as permitted by the pin and slot connection.

7. A fuze in accordance with claim 6, wherein said arm, at said other side of said connection, is provided with a projection moveable in an arcuate slot' in the housing having limit stops at its ends, corresponding to safe and fire positions, the rotor spring urging said projection against the safe end limit stop, preventing the arm from moving in the event of unauthorized impact while the rotor is at safe position.

8. A fuze in accordance with claim 7, including a stop pin carried by the rotor and engageable with the tire end limit stop. 

